Simplify RF Design forFitness and HealthcareWearables

By Majeed Ahmad, Contributing Writer

Health-based wearable solutions are coming of age, thanks to the silicon platforms that integrate
ultra-low-power wireless connectivity
with high-resolution analog front-end
circuitry and a viable processing portfolio based on ARM cores.

The wireless connectivity is in full
bloom to help create a myriad of
wearable medical devices ranging from
heart-rate monitors and fitness trackers,
to in-ear thermometers (Figure 1). There
are also disposable smart patches and
biosensors aiming to replace billions of
wired wearable sensors for vital signs
monitoring and electrocardiogram leads.

The ultra-low-power RF platforms
are a key building block in medical
wearable designs, and this article aims
to provide a detailed treatment of what
matters the most in the design and
integration of RF subsystem into a clinical-grade wearable device.

Wireless Connectivity

A robust wireless connection is imperative for high-accuracy data transport
in ultra-small healthcare devices. And
the choice of the wireless connectivity mechanism is intertwined with
key wearable design considerations:
bandwidth, power consumption, and
communication range.

So far, most wearables are runningon Bluetooth low energy (BLE)—for-merly known as Bluetooth Smart—andmedical wearables, are no exception.

The energy-efficient wireless technology
allows wearable products to be powered
by a single Li-ion coin cell battery for
months, even years in some cases.

Then, there are complementary technologies like ANT1, a Bluetooth alternative developed by Garmin used for the
monitoring of heart rate, distance, and
speed. The ANT wireless networking
technology consumes half the channel
frequency as compared to BLE and is
highly popular in cycling and fitness
brands.

Likewise, some BLE chipsets are concurrently supporting Thread1 1.1 specification, another BLE substitute that
connects wearable devices in a secure
and scalable manner. It’s an IPv6-based
mesh networking protocol that is similar
to Wi-Fi but is designed for low-power
and resource-constrained devices.

What’s next? The wearable devices
operating in clinical environments can
also communicate with specialized data
hubs using the 2. 4 GHz proprietary
wireless; these hubs are then connected
to Wi-Fi hot spots inside the medical
facilities.